1) install/activate [extension by Piwigo Team] LocalFiles Editor from screen [Administration > Plugins > Manage]

2) open [Administration > Plugins > LocalFiles Editor > Local config] and paste the following code:

<?php
$conf['allow_random_representative'] = true;
?>

Nakre wrote:

is that working only for the albums that has sub-albums ? coz so far thats what i see if an album has not sub one doesnt seem changes randomly.

Sorry Nakre, my answer was not complete (I don't use this configuration setting very often).

Once you've set $conf['allow_random_representative'] = true, then you have to perform a "Delete Representant" action on each category. You can also perform the following SQL query:

UPDATE piwigo_categories SET representative_picture_id = NULL;

ah plg would the representants change as the random image with abt time 10 secs etc, without refresh needing ?